RIOTS in Nauru are expected to have caused tens of millions of dollars worth of damage after asylum seekers destroyed buildings in chaotic scenes overnight.

Fire destroyed many of the detention facility's buildings, including the 616-room accommodation block.

A spokeswoman for the Department of Immigration said the massive damage bill was caused by 150 of the centre's 545 residents.

There remains 129 asylum seekers in the watch house of the Nauru police station after the country passed legislation overnight to enable police to hold people of interest to their investigations for up to seven days without being charged, the spokeswoman said.

"The ringleaders apprehended at the site will be questioned by police about allegations of property damage, destruction of property and riotous behaviour. If ultimately convicted of these charges under Nauru law, the penalty is one to seven years jail,'' she said.

"The Nauru Secretary of Justice and Border Control has said Nauru will prosecute people to the full extent of the law.''

The department is arranging to fly back to Australia "any staff who have been affected by this experience and feel like they need to leave''.

None of the staff were injured but four asylum seekers were taken to hospital, three with minor injuries and one due to a pre-existing condition, the spokeswoman said.

The asylum seekers will now be housed in tents and marquees at another site on the island where the department is in the process of building an accommodation block for families and single men.

The spokeswoman said there were no concerns about food supply as the kitchen and recreation buildings at the detention centre were "still standing''.

As well as the accommodation block, the rioters destroyed the dining room, offices and the health centre, she said.

Opposition immigration spokesman Scott Morrison said people had suffered "very serious injuries'' during the riot, although it was unclear what, if any, injuries had been suffered by any detainees.

"I understand the situation is still very unsettled,'' he said, adding the incident, over processing delays, had been brewing for some time.

"There is a pattern here in terms of how this government manages things: it always ends in chaos.''

Mr Morrison described it as "a very disturbing situation''.

He said everyone who was located at the centre would now have to be relocated to the other site on the island, which was being built for family accommodation.

Local man Clint Deidenang said the situation on the island had "calmed down'' this morning and residents were upset by the damage caused during the overnight chaos.

"Security guards and workers are cleaning up the area (at the detention centre). It's the biggest chaos in Nauru I've ever seen,'' Mr Deidenang said.

"(The people of Nauru) just want to see peace.''

Earlier Mr Deidenang described the incident as the "biggest baddest ever in Nauru''.

He tweeted most of the detenion centre's buidlings had burned down.

''Smokes can be seen from the torched story buildings. All buildings damaged except for one giant building. 95% buildings burned out.''

Mr Deidenang this morning told ABC radio up to 1000 local Nauruan men carrying machetes and steel pipes arrived to help police armed with batons and shields prevent the mostly Iranian asylum seekers from breaking out.

''There was massive confusion and commotion,'' Deidenang said.

''There was lots of flying debris, flying objects, stones - anything that could be thrown by hand.''

Yesterday he said the chants could be heard coming from inside the detention centre from about 6pm.

Mr Deidenang said he heard up to eight explosions before the flood lights outside the detention centre were smashed.

He tweeted: "Massive fire broke out from with the camp. I can see flames and smokes over the tree tops from my position.''

Witnesses tweeted reports of violent confrontations between Iranian asylum seekers and "deputised" local residents - and there were claims that 15 guards and a police officer had been injured. There were also reports that detention centre staff had temporarily been taken hostage.

Around around 300 of the 500 detainees were said to have escaped.

A Nauruan MP earlier took to state television to call for big, strong men to head to the processing camp as Nauruan riot police were overwhelmed.

Hundreds of civilians responded to their leaders' call and there had been reports that a bus carrying detention inmates away had been attacked.

Three interpreters and three medical staff were reportedly held for an hour before being released but it was unclear if they had been injured.

There was confusion over the motivation for the riot, with some reports from Nauru suggesting it was linked to the Mr Rudd's hard line announcement. This has not been confirmed, but chants of "freedom" were heard at the centre as the riot ignited.

Witness Daisy Lewis reports on Twitter that "two districts'' had been evacuated after the explosions.

She said all Nauruan males had been called in to help bring the riot under control.

A NOTE ABOUT RELEVANT ADVERTISING: We collect information about the content (including ads) you use across this site and use it to make both advertising and content more relevant to you on our network and other sites.